Metabolomic signatures of probiotic secretomes reveal strain-specific biofunctional potential: insights from Lacticaseibacillus rhamnosus R0011 and Bifidobacterium longum R0175.

Probiotic secretomes are cell-free byproducts of bacterial growth, which contain bioactive metabolites. These metabolites have antioxidant and anti-inflammatory effects and mediate the host-microbe and microbe-microbe interactions. However, the metabolomic profiles of probiotic secretomes are strain-specific and have not been fully investigated. Untargeted metabolomic analysis was used to characterise the metabolomic profiles of Lacticaseibacillus rhamnosus R0011 (R11) secretome (LR) and Bifidobacterium longum R0175 (R175) secretome (BL). LR and BL had distinct metabolomic profiles. LR exhibits a greater relative abundance of branched-chain hydroxy and aromatic lactic acids, mannitol/sorbitol, mevalonate and flavin mononucleotide. BL is characterized by higher relative abundance of indolelactate, γ-glutamylamino acid, niacin-related metabolites, and organic acids in the citric acid cycle. This study is the first to reveal distinct metabolomic signatures of two widely used probiotic species, providing new insights into their strain-specific roles in host health and microbiome modulation.